This organization has a flag: blue with flags of Slav states arranged in circle.
The organization's web page states: "The Flag of the Slavic Union is comprised of thirteen flags: the twelve flags of the Slavic States, plus the flag of the Wends, the Sorbs of Lusatia. This group, recognized as a national minority in Germany, are a separate Slavic nation with their own unique language and their own national symbols, including a flag. Because of this we include them in the flag of the Slavic Union. We also acknowledge here the Croats of Gradiąte, an original Slavic minority in Austria, with their own written language slightly different from the official Croatian language."
The headquarters of the Slavic Union is based in Helsinki, Finland. The first filial of the Slavic Union it was founded in Serbia, and we are proud to inform you about it. About Burgenland Croats and "Bunyevtzi", in the explanation about the flag on the filial site, we probably didn't explain correctly. After the flag there should be one small table, as on where we just acknowledge Burgenland Croats as a very original Slavic minority out of the official Slavic states. It does not mean we priorize Burgenland Croats above others, but it is just interesting that they are very original and they keep their identity far away from Croatia surrounded by the Romano-Germanic world.